This invention relates to a fuel distribution system for an internal combustion engine.
In known vertical shaft internal combustion engines, the fuel nozzles for the individual cylinders are connected to a mixing chamber adjacent the intake valves, in a manner as disclosed in U.S. Pat. No. 4,227,492. During the operation of such internal combustion engines the intake valves open to allow air and fuel to flow into supply chambers on the intake stroke of the pistons and close on the compression stroke of the pistons to prevent the mixture of air and fuel from being expelled back into the mixing chambers.
Normally the intake valves of such internal combustion engines are reed valves. A portion of the fuel-air mixture that must be transmitted to the supply chambers contact the reed valves. Often times at low engine speeds the atomized fuel atoms contact the reed valves and are combined with fuel collected on the reed valves to produce dropplets of fuel. Such dropplets accumulate around the reed valves and should they be drawn into the combustion chamber, the result is too rich a fuel mixture for the operation of the engine. Since some flow of fluid occurs, because the reed valves do not close immediately on movement of the pistons, on the down stroke by the combustion force produced by ignition of the fuel-air mixture in a combustion chamber, a portion of the fuel supplied to operate one chamber is often added to the fuel supplied to an adjacent chamber. This additional fuel in the form of either dropplets or atomized fuel is most noticeable when an internal combustion engine is operating at a low or idle speed. For example, in vertical shaft engines it has been found that the upper combustion chambers receive a leaner fuel-air mixture while the lower combustion chambers receive a richer fuel-air mixture even though both are supplied with the same volume of fuel per cycle of operation. The retention members on the intake manifold disclosed in U.S. Pat. No. 4,227,492 prevents intermingling of fuel between adjacent mixing chambers, however, dropplets of fuel can still be produced through the action of the reed valves engaging in the atomized fuel.